The S-IC (pronounced "ess one see") was the first stage of the Saturn V rocket. The S-IC first stage was built by The Boeing Company. Like the first stages of most rockets, most of its mass of over two thousand metric tonnes at launch was propellant, in this case RP-1 rocket fuel and liquid oxygenoxidizer. It was 42 meters tall and 10 meters in diameter, and provided 33,000 kN of thrust to get the rocket through the first 61 kilometers of ascent. Of the five F-1 engines, one was fixed in the center, while the four on the outer ring could be hydraulically turned to control the rocket.

MSFC built the first three test stages (S-IC-T, the S-IC-S, and the S-IC-F) and the first two flight models (S-IC-1 and -2). They were built using tools produced in Wichita.

It took roughly 7 to 9 months to build the tanks and 14 months to complete a stage. The first stage built by Boeing was S-IC-D, a test model.

Components

The largest and heaviest portion of the S-IC was the thrust structure, weighing 21 metric tons. It was designed to support the thrust of the five engines and redistribute it evenly across the base of the rocket. There were four anchors which held down the rocket as it built thrust. These were among the largest aluminum forgings produced in the U.S. at the time, 4.3 meters long and 816 kilograms in weight. The four stabilising fins withstood a temperature of 1100 °C.

Above the thrust structure was the fuel tank, containing 770,000 liters of RP-1 fuel. The tank itself had a mass of 11 metric tons dry and could release 7300 liters per second. Nitrogen was bubbled through the tank before launch to keep the fuel mixed. During flight the fuel was pressurized using helium, that was stored in tanks in the liquid oxygen tank above.

Between the fuel and liquid oxygen tanks was the intertank.

The liquid oxygen tank held 1,204,000 liters of LOX. It raised special issues for the designer. The lines through which the LOX ran to the engine had to be straight and therefore had to pass through the fuel tank. This meant insulating these lines inside a tunnel to stop fuel freezing to the outside and also meant five extra holes in the top of the fuel tank.